1. Field of the Invention
The present invention relates to an image forming device for forming images on a recording medium, and more particularly to an image forming device that includes multiple trays, selects one of the multiple trays, and forms images on a recording medium stored in the selected tray.
2. Related Art
A conventional image forming device has a printing means for forming an image on a recording medium, multiple trays for storing recording medium, a selection means for selecting one of the multiple trays, and transportation means for carrying a recording medium stored in the selected tray to the printing means. The printing means forms an image on the recording medium supplied from the selected tray.
One type of such a selection means automatically selects one of multiple trays that holds the appropriate size of recording sheet. For example, a laser printer disclosed in Japanese Patent-Application Publication No. HEI-11-157681 automatically selects a tray that holds the size of sheet appropriate to image data received from a host computer, and a photocopier disclosed in Japanese Patent-Application Publication No. HEI-11-174908 automatically selects a tray that corresponds to a document size detected by sensors. Various sizes of recording sheet, including metric and US paper sizes, can be used in the photocopier of Japanese Patent-Application Publication No. HEI-11-174908.
The tray selected by the selection means of these image forming devices could be empty. However, Japanese Patent-Application Publication No. HEI-11-174908 discloses nothing about what to do when there is no recording sheet in the selected tray. In the laser printer of Japanese Patent-Application Publication No. HEI-11-157681, when there is no recording sheet in the initially selected tray, a different tray is selected. Then, if the newly selected tray contains the same size of recording sheet, a recording sheet is fed from the newly selected tray. However, if the same size of recording sheet is not held in the newly selected tray, then printing operation is halt, and the user is prompted to load the same size of recording sheet into the tray. That is, the same size of recording sheet must be stored in each tray.
However, storing the same size of recording sheet in each tray is not very useful for an image forming device that handles documents and image data of various sizes. Furthermore, depending on how the image forming device is used (that is, for a functional purpose, such as receiving faxes, photocopying, or printing data from a personal computer, or a task-oriented purpose, such as a final copy or test print), it may be desirable to use a different size of recording sheet than is first selected. This applies not only to the sheet size, but also the type of recording sheet (such as bond paper, OHP film, or special-purpose paper, and various paper thicknesses).